Compositions and processes for providing amino acids and carbohydrates in ruminant feed

ABSTRACT

Methods and compositions for improved ruminant diets are disclosed. The invention relates to the use of metal ion/metal ion salts in ruminant feed, at levels from about 0.25 to about 1 g/kg dry matter, in any ruminant diet, for improvement of bypass protein content, as well as to influence the rate of rumen starch digestion and the flow of starch to the duodenum.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of priority to U.S. ProvisionalApplication No. 60/324,593, filed Sep. 25, 2001, which application hasbeen incorporated by reference in its entirety.

STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT

[0002] Not applicable

REFERENCE TO MICROFICHE APPENDIX/SEQUENCE LISTING/TABLE/COMPUTER PROGRAMLISTING APPENDIX

[0003] Not applicable.

BACKGROUND OF THE INVENTION

[0004] The importance of rumen digestion of protein in the productiveefficiency of ruminant diet formulations has been recognized for aconsiderable time. Feeds entering the rumen environment are digestedwith variable efficiency, such that the contribution of protein andenergy to the rumen fermentation, or alternately to the animal via rumenescape followed by intestinal digestion and absorption, varies widelyamong feedstuffs. The variability in feeding value amongst feeds andanimal classes has led to the development of diet evaluation softwareincorporating digestion rates relating to a variety of nutritionallyimportant protein and carbohydrate fractions (Dairy NRC 2001; Fox, etal., 1992.).

[0005] As summarized in such computer programs, the specific feed valueof a dietary ingredient varies both with animal productivity and dietformulation or composition. As animal productivity increases, so do thenutritional requirements for amino acids, metabolizable protein andenergy. At low levels of production, nutrition demands are more readilysatisfied by the end products of rumen fermentation, as well as volatilefatty acids as energy sources, and by the use of microbial protein tosupply metabolizable protein and amino acids. At elevated productionlevels the gross efficiency of nutrient digestion decreases, increasingthe proportion of nutrients escaping rumen fermentation. The specificefficiency of microbial protein produced in the rumen is somewhatvariable and difficult to predict, but does not increase sufficiently,such that rumen fermentation is unable to supply the quantity ofmetabolizable protein required to meet productive demands. Thisshortfall of rumen microbial protein production increases the dietarydemand for rumen bypass protein. Thus, research efforts aimed atachieving continued increases in ruminant productive level andefficiency have emphasized the importance of the nutrients which escapeor bypass rumen fermentation. Therefore, a number of rumen escapeproteins are now available in the marketplace.

[0006] A parallel development to rumen escape protein has been anincrease in dietary energy density to meet the energetic demands ofincreased production. For high production situations, this has increasedthe level of rumen fermentable carbohydrate in diets by raising starchlevels. Increased feeding of starchy ingredients has led to increasedconcerns relating to rumen acidosis and loss of productive efficiencyfrom the rumen.

[0007] A variety of methods have been used to reduce the rumenavailability of vegetable protein. U.S. Pat. No. 3,619,200 proposes arumen-inert coating of vegetable meal for protection against rumenmicrobial digestion. Treatment of feeds with tannin, formaldehyde, orother aldehydes can denature the protein and reduce ruminal fermentation(see U.S. Pat. No. 4,186,213), and rumen digestion of protein can bereduced by heating (Tagari et al., Brit. J. Nutr. 16:237-243 (1982)).

[0008] Hudson, et al., J. Anim. Sci. 30:609 (1970) presents anexperiment comparing evaluating the effect of heating on SBM on the postruminal nitrogen utilization by lambs. The results indicated slowerprotein digestion by rumen microflora.

[0009] Endres, et al., 1996, and Heitritter, et al., 1998 (U.S. Pat.Nos. 5,508,058 and 5,824,355, with references) summarize the procedurescommonly used for production of heat-treated vegetable meals.

[0010] The patents of Meyer, 1987, 1988, and Endres, et al., 1996 (U.S.Pat. Nos. 4,664,905, 4,664,917, 4,704,287,4,737,365, 5,508,058) disclosethe use of zinc salts to protect animal feed protein from rumendegradation.

[0011] The patents of Meyer, 1987 and 1988 (U.S. Pat. Nos. 4,664,905,4,664,917, 4,704,287, 4,737,365) established the use of relatively highlevels of zinc salts to improve protein utilization in beef and dairycattle and sheep. Incorporation levels of zinc were from 0.25 to 1.3%dry weight or alternately 0.005 to 0.0294 parts zinc ion per unitprotein in a protein dry blend.

[0012] Endres, et al., 1996 (U.S. Pat. No. 5,508,058) disclose a methodto produce heat treated vegetable protein incorporating zinc at a lowerlevel than previously discovered (0.003 to 0.008 parts zinc per partprotein). As discussed in that disclosure, the use of lower zinc levelsis beneficial in reducing the excretion of zinc into the environment viaanimal manure while retaining efficacy of reducing rumen proteindigestion of the protein feed.

[0013] 1. Field of the Invention

[0014] The present invention relates to methods and compositions for theimprovement of ruminant diets. More specifically, the present inventionrelates to the use of metal ions and/or their salts in feed to improveproductive efficiency where alterations in rumen digestion rates ofprotein or starch are desirable.

[0015] 2. Background Art

[0016] Not applicable.

BRIEF SUMMARY OF THE INVENTION

[0017] The present invention relates to improved animal feedcompositions comprising one or more metal ion(s) or metal salt(s) at aconcentration of from about 0.25 gram to about 1 gram per Kilogram offeed dry matter. The present invention further relates to ruminant dietformulations comprising such improved feeds, and the process for makingsuch improved feed compositions. The present invention also furtherrelates to a process for improvement of the productive efficiency of aruminant diet by providing to a ruminant a diet comprising such animproved animal feed.

[0018] This invention has a primary objective of retaining the efficacyequivalent to previous zinc use while further reducing the levels ofzinc needed.

[0019] A further objective of this invention is to utilize zinc singlyand in combination with other metals or metal salts to modify the rumendegradation of both protein and carbohydrates.

[0020] Previous work has focused on the ability of dry mixtures of metalsalts to protect protein-containing feeds as part of protein supplementsor complete feeds. In early efforts, manganese was evaluated for itsability to slow rumen protein digestion and was discounted in favor ofzinc. However, the present inventors have found that, surprisingly, theuse of zinc salts with manganese salts (manganous sulfate) inart-recognized methods of use leads to an unexpected synergisticreduction of rumen protein digestion, where the decrease in proteindegradation is greater than that expected based on the levels of eitherelement singly. Furthermore, a similar synergy has been achieved byadding soluble iron salts to the blend. Unexpectedly, the form of ironis particularly important, with ferrous iron preferred to other electronstates. Recent research also demonstrates the ability of zinc salts andmetal mixtures to influence the rate of rumen starch digestion and theflow of starch to the duodenum of dairy cattle.

[0021] In addition, the present invention takes advantage of thesurprising finding that the effects of metal salts may be generalized toall dietary ingredients contributing protein, including forages,although the magnitude of effect is ingredient specific. Thus, thepresent invention relates to the use of metals salts, in combinationwith both amino acid formulation, and the formulation of the entirediet, to influence the amino acid and nutrient profile appearing at theduodenum, allowing increased animal performance.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

[0022] Not applicable.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention proposes the use of zinc in combinationwith heat processing at levels from about 0.25 to about 1 g per kg drymatter (DM) of the feed (meal or forage) being utilized. Further,combinations of water soluble salts (preferably sulfate salts, althoughit is important to note that all water soluble salts, and combinationsof metals or metal salts, may be used in the practice of the invention),of zinc, manganese and iron (preferably the ferrous form of iron) may beprovided in animal diets singly or in combination at a totalconcentration of between about 250 and about 750 ppm of diet DM toincrease rumen escape of diet protein, to reduce ruminal ammoniaproduction, and to reduce the fermentation rate of dietary starch. Inaddition, when combined with dietary formulation of amino acid profiles,incorporation of water soluble zinc, manganese, or iron salts may beutilized to modify the profile of amino acids appearing in thepost-ruminal digesta flow.

[0024] The present invention may be practiced in any ruminant diet. Toobtain the desired results, diets may be formulated to contain singlemetal ion forms or combinations of metal ions at a concentrations fromabout 0.25 to about 1 g/kg of diet dry matter. In practice metal saltsmay be incorporated directly into the animal diets, or mixed intocommercial supplements or liquid feeds. As those of skill in the artwill recognize, absolute concentrations of the metal salts incorporatedinto supplements will be dependent on the dietary inclusion rate of thesupplemental feed. For example, and not by way of limitation, to ananimal eating 25 kg dry matter per day, a mineral supplement or liquidfeed offered at 1 kg dry matter per day may be expected to containbetween 6.25 to 25 g metal ion per kg of the supplement. If thesupplemental inclusion rate were to increase to 10 kg dry matter per daythe corresponding concentrations would be 0.625 to 2.5 g metal ion perkg of supplement dry matter.

[0025] This invention may also be used to improve the bypass proteincontent of animal feeds in combination with moist heat treatment. Forexample Heitritter, 1998, discloses the use of a moist heat treatmentprocess. To utilize this invention in combination with heat treatment ofprotein meals, zinc or metal combinations may be blended into theprotein meal entering the process at a rate to obtain from about 0.25 toabout 1 g of metal ion per kg of feed dry matter, utilizing either drymixtures or liquid application of salts. Alternately, the metal blendsmay be incorporated into the feed ingredient after the initial cookingprocess but prior to the drying of the final mixture.

[0026] During the experimental work related to development of thisinvention an interaction between processing method and zincconcentration was determined which allowed for the reduction of zincconcentration to between about 0.25 and about 1 g/kg of feed material,or to a level of about one-third the amount previously reported. Table 1presents the results of a test addressing the interaction of moist heattreatment of soybean meal and zinc application. The expectation at thetime was that the response in rumen undegradable protein (RUP) requiredzinc levels above 1300 ppm in meal DM. Surprisingly, however, there wasa clear relationship between zinc concentration and bypass proteincontent/RUP even at lower than expected metal concentrations. TABLE 1Influence of zinc and heat treatment on the rumen undegradable proteincontent (RUP) of soybean meal Sample Zinc, ppm RUP, % CP 4 262 66.5 14472 67.9 25 1010 69.1 36 1721 70.2

[0027] In a second embodiment, experimental work by the presentinventors has derived improvements over the state of the art by the useof combinations of zinc and manganese or combinations of zinc, manganeseand ferrous iron to influence rumen fermentation and animal performance.These improvements occur when metals are provided at concentrationsranging from about 250 to about 1000 ppm total metal ion in diet DM.Specifically, dietary inclusion of metal combinations has been shown toreduce rumen protein digestion (increase RUP), reduce ammonia releasefrom protein and reduce milk urea nitrogen levels, and slow the rate ofrumen starch digestion. Thus, depending on diet formulation methods,metal addition may be used to influence the profile of nutrientsappearing at the duodenum for absorption.

[0028] Having provided a general description, the invention will now bemore readily understood through reference to the following examples,which are provided by way of illustration, and which are not intended tolimit the present invention.

EXAMPLES Example 1

[0029] In vitro digestion of alfalfa silage, a complete dairy pellet,and dairy total mixed ration TMR) was performed using an artificialrumen system (Ankom Daisy System, Ankom Technology, Fairport, N.Y.) in apartial factorial arrangement of treatments incorporating zinc ormanganese, at two levels, singly or in combination, to evaluate effectson rumen protein digestion. Metals were incorporated at 150 or 300 mg/L.As shown in Table 2, zinc has a general effect on protein digestionwhile the effect of manganese is more moderate. The ‘Additive’ columnpresents the expected results based on a simple additivity of themanganese and zinc concentrations. The combination of zinc and manganesereduces protein digestion in a manner similar to the zinc only treatmentalthough the level of zinc has been reduced by 50%. These data extendedprevious findings, demonstrating that zinc and the zinc-manganeseaddition improved the rumen bypass protein content of alfalfa forage anddairy TMR samples as measured in the artificial rumen system (Table 3).Previous efforts focused on the digestion of high protein feeds such asoilseed meals. TABLE 2 Average rumen undegraded protein, % of protein,for all samples Metal inclusion Zinc (Zn) Manganese (Mn) ‘Additive’Zn/Mn, 50:50  0 40.2 — — — 150 mg/L 45 43.2 42.7 44.2 300 mg/L 48 42.545.3 47.4

[0030] TABLE 3 Effect of dietary metal addition on rumen undegradedprotein Metal inclusion Zinc (Zn) Manganese (Mn) Zn/Mn, 50:50 DairyConcentrate Feeds  0 47.8 150 mg/L 61.4 50.9 55.7 300 mg/L 63.5 52.367.4 Alfalfa Haylage  0 24.6 150 mg/L 24.4 26.1 31.3 300 mg/L 28.2 24.825.5 Dairy total mixed ration  0 48.3 150 mg/L 48.9 51.8 46.3 300 mg/L52.5 51.5 48.3

Example 2

[0031] Samples of soybean meal (SBM), heat treated soybean meal, canolameal, heat treated canola meal, and cottonseed meal were fermented invitro in combination with zinc sulfate, or ferric or ferrous ironsulfate. In those fermentations containing metal, metal ions were addedto obtain a concentration of 150 mg/L. Relative to controls with nometal addition all metals increased RUP content measured after 16 h offermentation (Table 4). Surprisingly, the ferrous form of iron wassubstantially more effective than the ferric ion for decreasing rumenprotein digestion. TABLE 4 Mean RUP and Metal Effects for IndividualIngredients Treatment 50:50 Zinc Ferrous and Ingredient Control FerricIron Iron Zinc Manganese SBM 28.6^(a) 29.1^(a) 42.9^(b) 56.4^(c) 59.7Canola 46.5^(a) 51.6^(ab) 57.7^(b) 57.3^(b) 66.3 Cottonseed 56.3^(a)58.4^(b) 62.1^(bc) 64.4^(c) 66.3 Heated Canola 79.7^(a) 81.1^(a)83.5^(b) 85.2^(b) 85.9 Heated SBM 78.6^(a) 81.7^(ab) 83.9^(b) 85.2^(b)85.6

Example 3

[0032] Lactating Holstein dairy cows were randomly divided into twogroups based on production, days in milk and parity. Both groups ofanimals received diets based on alfalfa and corn silage supplementedwith a commercial concentrate. The treatment diet was formulated toprovide 300 ppm of a 50:50 blend of zinc and mangenous sulfate.Calculated soluble protein supplied was 40% of dietary crude protein(CP). The level of heat treated soybean meal was reduced in the metalcontaining diet to account for the effects on protein digestion(calculated as two percentage decrease in RUP, % of dietary CP). Bothdiets were formulated to contain RUP of a similar amino acid profile.There were no differences in milk production or milk component levels.There was a significant decrease in milk urea nitrogen levels with metalinclusion. These data demonstrate the effects of metal ions onperformance by lactating cows, and are comparable to prior art in whichzinc alone was used. The difference in the present example is thatcombining metals affords efficiency with lower concentrations of zincthan expected being necessary in the final feed product. TABLE 5 Effectsof Zinc and Manganese on Milk Yield by Lactating Cows Item Control Zn/MnSE P = Diet CP 19.05 18.98 — — Diet Zn, ppm 88 216 — — Diet Mn, ppm 78211 — — Milk, kg/d 35.6 35.6 .63 .86 Milk Fat, % 3.49 3.43 .06 .52 MilkProtein, % 2.9 2.92 .02 .24 MUN¹, mg/ml 14.9 14.1 .20 .02

Example 4

[0033] Individually fed crossbred wether lambs were fed diets containing14% CP (as a negative control) or 16% CP with low or high RUP content toexamine the feeding of divalant metals singly or in combination. Bypassprotein content was increased by feeding higher amounts of heat-treatedsoybean meal. In the 16%, Low RUP diet, the following metal additionswere tested: 500 ppm Zn; 250 ppm Zn:250 ppm Mn; and 170 ppm Zn: 170 ppmMn: 170 ppm Fe. All metals were added in the sulfate form, and iron wasin the form of ferrous sulfate. Feeding the 16% CP: High RUP diet oradding metals to the 16% CP: Low RUP tended to decrease gain and feedefficiency with only small effects on feed intake relative to thatobtained with the 16%, low RUP diet (Table 6). TABLE 6 Performance oflambs receiving zinc, or zinc, manganese, iron combinations High CP HighCP High CP Negative High CP High CP Low RUP Low RUP + Low RUP + DietDescription Control Low RUP High RUP Zn Zn/Mn Zn/Mn/Fe CP, % 14.0 16.016.0 16.0 16.0 16.0 RUP, % 5.0 5.2 6.4 5.2 5.2 5.2 SEM Initial weight,kg  24.4  23.2  24.7  24.7  24.0  23.9 1.2 42 day weight, kg  40.1^(b) 44.2^(a)  43.7^(a)  43.8^(a)  42.7^(a,b)  41.8^(a,b) 1.4 DMI¹, kg/day 1.50^(b)  1.59^(a,b)  1.62^(a,b)  1.66^(a)  1.51^(b)  1.49^(b) 0.05Total Gain, kg  15.84^(b)  20.44^(a)  18.96^(a)  18.81^(a)  18.88^(a) 18.30^(a) 1.12 ADG¹, g/day 394^(c) 486^(a) 464^(a,b) 451^(a,b)446^(a,b) 429^(b,c) 17 G/F¹ × 100  26.5^(b)  30.7^(a)  28.7^(a,b) 27.3^(b)  29.6^(a)  28.9^(a,b) 1.1

[0034] Although the effects of additional RUP were negative on animalperformance for this model animal system, the data substantiate the useof low amounts of zinc, or combinations of zinc manganese and iron toinfluence rumen protein digestion. The level of response to metaladdition was equivalent to that of the heat treated SBM.

Example 5

[0035] A six week lactation study was conducted using 59 Holstein cowsto test the effects of zinc on performance and the interaction withdietary bypass protein content (RUP). Treatments were administered byadjusting the RUP in the 20% CP dairy complete feed from 8.0% (Control)to 9.0% RUP (Control+RUP) and zinc from 245 ppm (Control) to 1020 ppm ofzinc (Control+Zinc). This provided 755 ppm zinc from zinc sulfate in aratio of 0.003 part zinc ion per part protein in the complete feed. Thesource of RUP was a combination of heated soybean meal, corn glutenmeal, and distiller dried grains. Increasing dietary zinc numericallyimproved milk yield by 1.1 kg/d or 3.4%. Feeding higher amounts ofbypass protein did not improve yield. Without intending to be limited bytheory, these results suggest that zinc may be affecting the supply ofnutrients besides protein that are critical for lactation. Zinc maydecrease ruminal digestion of fiber and nonfiber so that more of thesecomponents are supplied to the intestines. This phenomena may bedetrimental in the case of fiber but potentially beneficial in the caseof nonfiber (e.g., starch) because energy supply to the cow may beimproved. The potential for zinc to shift the site of carbohydratedigestion from the rumen to the intestines has not been describedpreviously. TABLE 7 Milk production of cows receiving zinc or RUP ItemControl Control + Zn Control + RUP Milk, kg/d 32.1 33.2 31.8 Milk Fat, %3.30 3.25 3.33 Milk Protein, % 3.21 3.20 3.25

Example 6

[0036] A study was performed to examine whether increasing dietary zincand/or RUP content would affect ruminal digestion and the flow of aminoacids to the small intestine of lactating dairy cows. Cows were fed aTMR containing low and high amounts of RUP and low or highconcentrations of zinc (zero or additional 250 ppm zinc from zincsulfate). The concentration of RUP in high and low RUP diets weremanipulated by changing the proportions of low RUP feeds (soybean meal,canola) and high RUP feeds (heated soybean meal, corn gluten meal).Feeding higher amounts of zinc shifted site of nutrient digestion fromthe rumen to the small intestines. A surprising observation was theeffect of zinc on rumen digestion of starch. In both the low and highRUP diets, feeding higher concentrations of zinc reduced the digestionof starch in the rumen. TABLE 8 Effects of RUP level and zinc on rumennutrient digestion Low RUP, Low RUP, High RUP, High RUP, Item Low ZnHigh Zn Low Zn High Zn Dry matter intake, 22.8 21.8 21.5 22.2 kg/dIntestinal Amino Acid flows, g/d Lysine 187.2 183.3 182.6 200.0Methionine 51.6 49.0 56.1 58.2 Total Essential 1398 1331 1469 1601 AminoAcids Ruminal digestion, % of intake Organic Matter 54.1 47.3 45.5 45.5Neutral Detergent 33.5 22.0 24.0 24.8 Fiber Starch 67.0 53.6 64.3 52.8

Example 7

[0037] In vitro digestions of a complete dairy pellet, and a dairy totalmixed ration TMR) were performed using an artificial rumen system (AnkomDaisy system) to evaluate the effects of metal ions on rumen starchdigestion. Treatments formed a partial factorial arrangementincorporating zinc or manganese, at 150 or 300 mg/L of metal in the invitro media, singly or in combination, to evaluate rumen starchdigestion. Inclusion of zinc or the zinc and manganese combinationincreased the rumen undegraded starch measured at 16 h and decreased thecalculated kinetic rate for starch digestion. The decrease of in vitropH over the first 16 hours of fermentation was moderated by theinclusion of zinc or zinc-manganese blend as was the rate of decline.The total decline in pH over the 48 hour fermentations (initial pH—finalpH) was not statistically different. TABLE 9 Mean Effect of MetalAddition on In Vitro Starch Digestion and pH 50:50 Zinc + Item ControlZinc Manganese Manganese Main Effects¹ Concentration, mg/L 0 150 300 150300 150 300 SE Zn Mn Zn/Mn Rumen Undegraded 8.6 13.2 12.0 5.1 8.0 13.215.6 1.9 4.0 −2.0 5.8* Starch (16 hours), % Ammonia mg/dL 31.4 30.8 29.732.1 34.2 30.6 29.9 1.8 −1.1 1.8 −1.2 Initial pH 6.74 6.69 6.60 6.656.64 6.68 6.62 .03 −.1** −.1** −.09** pH at 16 hours −.37 −.35 −.28 −.28−.34 −.32 −.32 .03 .05* .05* .05* pH at 48 hours −.32 −.30 −.23 −.30−.27 −.30 −.25 .03 .05 .03 .05 Digestion Rates, % per hour RumenUndegraded −.135 −.096 −.098 −.137 −.132 −.105 −.102 .007 .038** 0.0.031** Starch (16 hours) pH Decline .233 .209 .205 .135 .247 .221 .220.04 −.027 −.043 −.013

Example 8

[0038] A study was conducted using four duodenally cannulated Holsteincows to investigate the effect of a zinc:manganese blend on the rumendigestion of starch and soluble fiber. Diets contained 10.9 kg alfalfasilage, 3.6 kg mixed hay, 1.4 kg hay pellets, 9. 1 kg completesupplement and 2.7 kg of com/soyhulls or beet pulp/soyhulls (non-foragefiber, or NFF). Dietary RUP was formulated to 32.5% of CP, and the RUPlysine and methionine was adjusted to a 3:1 ratio. Diets containingadded metal contained 400 ppm of metal added as 50:50 zinc andmanganese. In this experiment, numerical decreases in rumen starchdigestion were associated with greater rumen pH, altered volatile fattyacid (VFA) profile, and significantly increased microbial efficiency(Table 10). TABLE 10 Effects of non-fiber carbohydrate type and metaladdition on rumen nutrient digestion Diet P = Metal Corn NFF NFC andItem Corn NFF^(a) Zn/Mn Zn/Mn SEM source Zn/Mn NFC Dry Matter Intake,kg/d 20.2 18.8 17.7 20.2 .09 .55 .60 .10 Rumen Digestion, % intakeOrganic Matter 31.1 40.8 32.5 40.9 1.7 .01 .65 .63 Neutral DetergentFiber 33.4 43.0 27.6 35.5 8.0 .28 .42 .90 Starch 75.9 66.6 64.0 61.2 9.8.60 .56 .53 Duodenal flow Non-Microbial N, % N intake 57.5 52.3 50.045.0 3.4 .17 .10 .99 Microbial N, % N flow 48.8 46.5 56.1 59.2 2.9 .86.03 .32 Microbial Efficiency g of N/kg 32.4 24.6 36.2 31.8 1.3 .01 .02.18 organic matter digested Average Rumen pH 5.77 5.96 5.83 5.81 .13 .50.76 .42 Acetate:Propionate Ratio 2.60 2.80 2.96 2.72 0.09 .85 .12 .04

[0039] In view of the foregoing description and examples, those skilledin the art will be able to practice the invention, in its variousembodiments and equivalents, without undue experimentation, and withoutdeparting from the spirit and scope of the invention as defined in theappended claims.

What is claimed is:
 1. An improved animal feed composition comprising an animal feed containing one or more metal ion(s) or metal salt(s) at a concentration of from about 0.25 gram to about 1 gram per Kilogram of feed dry matter.
 2. The animal feed composition of claim 1 wherein the one or more metal ion(s) or metal salt(s) are selected from the group consisting of zinc, manganese, and ferrous iron, or water soluble salts thereof.
 3. The animal feed composition of claim 1 wherein the feed dry matter is selected from the group consisting of meal dry matter or forage dry matter.
 4. A ruminant diet formulation comprising the animal feed composition of claim
 1. 5. A process for the improvement of the productive efficiency of a ruminant diet, the process comprising providing to a ruminant a diet comprising an animal feed comprising one or more metal(s) or metal salt(s) at a concentration of from about 0.25 gram to about 1 gram per Kilogram meal dry matter.
 6. The process of claim 5 wherein the one or more metal(s) or metal salt(s) are selected from the group consisting of zinc, manganese, and ferrous iron, or water soluble salts thereof.
 7. A process for making an improved animal feed composition, the process comprising adding to the animal feed composition an amount of one or more metal(s) or metal salt(s) to give a final concentration of from about 0.25 gram to about 1 gram per Kilogram meal dry matter. 